Polish folk music was collected in the 19th century by Oskar Kolberg, as part of a wave of Polish national revival. With the coming of the world wars and then the Communist state, folk traditions were oppressed or subsumed into state-approved folk ensembles. The most famous of the state ensembles are Mazowsze and Śląsk, both of which still perform. Though these bands had a regional touch to their output, the overall sound was a homogenized mixture of Polish styles. There were more authentic state-supported groups, such as Słowianki, but the Communist sanitized image of folk music made the whole field seem unhip to young audiences, and many traditions dwindled rapidly.